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Sina Mirtorabi ( sina @ cisco.com). Tunnel Adjacency. Agenda. What is Tunnel Adjacency ( TA ) ? What does TA resolve ? Scenarios where TA is used How is TA established ? How data packet are forwarded ? TA configuration parameter. What is Tunnel Adjacency ?.
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Sina Mirtorabi( sina @ cisco.com) Tunnel Adjacency
Agenda • What is Tunnel Adjacency ( TA ) ? • What does TA resolve ? • Scenarios where TA is used • How is TA established ? • How data packet are forwarded ? • TA configuration parameter
What is Tunnel Adjacency ? • TA is a new proposal in order to solve intra-area / Inter-area path preference • It is basically a generalization of VL • It can force OSPF to take a desired path • It has on-demand area partition repair
What does TA resolve ? • Intra-area / Inter-area path preference • In H&S topology, it save the cost of adding additional interface between ABRs. • On demand partition repair to avoid segmented area, required when summarization is done.
Scenarios where TA is used ( sub-optimum path)
Scenarios where TA is used ( sub-optimum path)
Scenarios where TA is used ( sharing link for different areas )
How is TA established ? • As for VL, TA is configured between two ABRs having in common an area • when there is an intra-area path through transit area, the adjacency is established and announced in the area for which the TA is configured.
How data packet is forwarded ? • If ABRs have a direct link, data packet are sent without any encapsulation • If ABRs are multi-hop, data packet are encapsulated • Encapsulation is dynamic and user does not need to configure
TA configuration parameter • TA configuration parameter consists of - remote neighbor Router-ID - TA Transit Area ( TTA ) - The Area to which TA belongs • Optionally, encapsulation type and on demand partition repair
To Summarize • TA is a generalization of VL • It resolves VL limitations - TA link can belong to any area - Summarization is not affected - TA can go through Stub/NSSA • It has added value features - TA cost is configurable - TA on demand partition repair - Multiple TA through a given path
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